spoIID operon of Bacillus subtilis: cloning and sequence

The locus spoIID, involved in the sporulation of Bacillus subtilis, was cloned into derivatives of the temperate phage phi 105. Two recombinant phages were obtained which contain chromosomal DNA covering 1.6 kbp. They are both able to complement mutations spo-68 and spo-298. These mutations, which were believed to be in different loci, spoIID and spoIIC respectively, were shown to be closely linked, and both map at the position assigned to spoIID on the genetic map of B. subtilis. The sequence of 1656 bp carrying the spoIID locus was determined. Only one open reading frame was found; this codes for a protein of 343 amino acids. It is preceded by a ribosome binding site and possible recognition sequences for sigma 32- and sigma 29-RNA polymerases. Studies of the locus by means of integrational plasmid vectors defined the outer limits of the transcriptional unit. These results are completely compatible with the sequence data. The combination of sequence and mapping and the information obtained by the use of integrational plasmids confirm that the spoIID locus functions as a monocistronic operon.